Gas streams often carry particulate materials including heavy metals, toxic organic chemicals, and selected microbiological molecules such as viruses. Common filter media include layered materials containing fibers of substances such as fiberglass, metals, ceramics and polymeric compositions. These filter media typically are ineffective in filtering submicron particulates and can easily become loaded with accumulated particles that restrict fluid flow. They also typically are non-economical because they must be replaced rather frequently. Furthermore, even if the filter media have tight pore sizes, such as those using non-woven micron sized fibers, for example HEPA filters (high efficiency performance airfilter), there can be significant drawbacks. These filters tend not to be as durable. In addition, because of the large pressure drops across the filter media, only the first few layers of fibers are capable effectively of filtering particles.
Consequently, it is desirable to develop a filtration medium with improved capacity of filtering particles of micron and sub-micron dimensions. It is also desirable to develop a filtration medium with improved filtering efficiency by reducing the pressure drop across the medium. Providing a filtration medium that can filter microbiological molecules, such as viruses, is also desirable. Moreover, it is desirable to develop a filtration medium with anti-microbial properties, as well as with the capability to release substances such as medications.